The invention relates, in general, to an industrial truck with a drive part and a load part for handling packed or empty pallets, in accordance with the preamble of Claim 1 and, in particular, to an industrial truck for handling pallets of a certain format, such as those used in the commissioning sector and in the transport of piece goods.
Such an industrial truck is known from U.S. Pat. No. 4,101,040. The load part has two load arms in the form of fork prongs that are oriented in the travel direction, i.e. the longitudinal direction of the industrial truck, and can be raised vertically, with which loads such as pallets or goods packed on pallets can be handled. The term xe2x80x9chandlingxe2x80x9d includes activities such as picking up, transporting, and setting down a pallet, goods packed on a pallet, or a stack of pallets. Other examples of such industrial trucks are conventional manual forklifts, electric forklifts, wheel-supported stackers, counterweight stackers, or reach mast trucks. In order to pick up a pallet or goods packed on a pallet, the pallet is particularly provided with suitable recesses for engagement of the fork prongs of the industrial truck, for example of a stacker.
In the transport of piece goods, and in the commissioning sector of commercial facilities, the pallets used are predominantly pallets made of wood, with a certain format, particularly so-called euro-pallets with a length of 1200 mm, a width of 800 mm, a height of 150 mm, and a weight of about 20 to 30 kg. In such facilities, quite a large number of empty pallets that are not needed are often left behind on the floor after roll-out cycles have been completed, and until now, these had to be stacked, either manually or using one of the aforementioned commercially available industrial trucks, to form pallet stacks of 15 to 17 pallets, for example (corresponding to the inside height of a transport truck), that could be transported and loaded. Making such a stack by hand involves a high level of physical effort. For this reason, the empty pallets are usually handled with one of the aforementioned industrial trucks.
However, the use of conventional industrial trucks for handling empty pallets proves to be extremely inefficient, since the activities that are involved in this task can only be performed with a high level of time expenditure, and therefore result in high personnel costs. In order to stack several empty pallets that are lying around on the floor into a pallet stack, for example, using one of the aforementioned industrial trucks, first the truck is driven towards a first empty pallet and the fork prongs of the industrial truck are placed under the first pallet. Subsequently, the first pallet is raised to a certain height, by means of a vertical movement of the fork prongs. In this condition, the industrial truck is driven towards a second pallet, specifically in such a way that the first pallet is essentially aligned with the second pallet. Then the first pallet is set down on the second pallet. At this point in time, the fork prongs are still engaged with the first pallet. In order to place a third pallet onto the pallet stack that now consists of the first and the second pallet, or to place this pallet stack onto a third pallet, the industrial truck must therefore first be put into motion in such a way that the fork moves out of the first pallet. Subsequently, the fork is lowered. Now the second pallet that is located on the floor, or the third pallet, can be approached and lifted. Subsequently, the stated steps can be repeated.
Without discussing the matter further, it is evident that stacking a pallet stack that consists of 15 to 17 empty pallets, for example, requires a constant back and forth movement of the industrial truck, particularly because of the fork prongs that project in the direction of travel, i.e. the longitudinal direction, in order to move the fork from a pallet in a higher position into a pallet in a lower position, or vice versa. This is very time-consuming and is accordingly connected with high personnel costs. The same holds true for unstacking empty pallets that have already been stacked together to form a stack, which fundamentally takes place in the reverse sequence as stacking the empty pallets.
In order to guarantee problem-free handling during pallet storage in a high-shelf facility or in automatic pallet packing, the pallets furthermore are not allowed to demonstrate any damage, such as pieces splintered off, missing wooden parts, etc., since the damaged pallets cannot be transported, or can be transported only with restrictions, and might no longer be suitable for use in a high-shelf facility, because they might no longer meet the static requirements. Severely damaged pallets can therefore no longer be used. In order to keep the acquisition costs for new pallets low, a high level of pallet quality is therefore considered to be very important. For this reason, a person who is entrusted with the operation of conventional industrial trucks or, in general, with the handling of empty pallets, requires a certain amount of practice in order not to damage the pallets with the fork of a stacker while bringing the fork into place, and in order to accomplish the task to be performed within a reasonable amount of time.
Furthermore, in order for a pallet stack made up of 15 to 17 empty pallets to possess the necessary stability to prevent it from tipping to the side, and to allow it to be temporarily stored or loaded onto a transport truck to take up as little space as possible, the pallet on the top of the pallet stack, in each instance, must be precisely aligned with the pallet under it, in each instance. This again presupposes a certain level of experience in the operation of the industrial truck. The number of persons who are able to assure safe handling of pallets, using conventional industrial trucks, is therefore limited to specially trained personnel.
Other industrial trucks are known from the European Patent Application No. EP 0 045 553 A1 and the U.S. Pat. No. 3,861,535. EP 0 045 553 A1 particularly describes a device for handling several boxes arranged in a row, or several stacks of boxes arranged in a row, using two clamping plates that are arranged opposite one another and can be moved horizontally towards one another. U.S. Pat. No. 3,861,535 discloses a forklift truck with a forklift mechanism and a carrying device, which holds pallets or pallet boxes that have been picked up by the forklift mechanism and raised to a certain height at this certain height.
Proceeding from an industrial truck as known from U.S. Pat. No. 4,101,040, the invention has the task of creating an industrial truck designed for simple and efficient handling, particularly of pallets with a certain format, which also allows picking up and transporting loads packed on a pallet.
This task is accomplished by means of the industrial truck in accordance with the characteristics of Claim 1.
The industrial truck according to the invention particularly demonstrates a drive part and a load part, as is the case for a conventional industrial truck. The load part comprises two load arms, oriented in the longitudinal direction of the industrial truck, to hold a pallet that can be packed or empty. In conventional industrial trucks, as indicated initially, the load arms are usually structured as fork prongs, which are brought into engagement with recesses provided in the pallet, by means of a forward movement of the industrial truck, forming a positive lock. The load arms are therefore arranged in accordance with the distance between the recesses, i.e. at a distance that is less than the dimension of the pallet to be picked up, in the crosswise direction of the industrial truck. In contrast to this, the load arms of the industrial truck according to the invention are arranged on different sides of the pallet to be picked up, in each instance, viewed in the direction of travel, i.e. the longitudinal direction of the industrial truck, in other words at a distance that is greater, in the crosswise direction, than the dimension of the pallet to be picked up, and they each have a plurality of pallet holders spaced apart in the longitudinal direction, which can be aligned towards the pallet, which can be brought into or out of engagement with the pallet, in particular with the recesses provided on the pallet, by means of a movement perpendicular to the longitudinal direction. This movement perpendicular to the longitudinal direction can take place exclusively by means of a movement of the load arms. Likewise, however, a movement of the pallet holders provided on the load arms, or a combined movement of the load arms and the pallet holders is possible. Furthermore, the movement of the pallet holders can consist of a purely horizontal movement and a purely vertical movement that takes place, in each instance, perpendicular to the direction of travel, i.e. the longitudinal direction of the industrial truck. However, the movement of the pallet holders can also be achieved by means of a circular movement of the pallet holders, which can be broken down into a horizontal component and a vertical component perpendicular to the longitudinal direction.
Since picking up the pallet, viewed in the direction of travel, i.e. the longitudinal direction of the industrial truck, takes place by means of engagement on both sides of the pallet, it is advantageous that the engagement lengths of the pallet holders, which can be structured as fork prongs, as in the case of conventional industrial trucks, can be significantly reduced. In conventional industrial trucks, the fork prongs must be at least long enough so that they extend beyond the center of gravity of the pallet to be picked up, so that the pallet does not tip over forwards when it is lifted from the floor. This relatively long length of the fork prongs increases the risk of damaging the pallet while the fork prongs pass under it. However, this risk is significantly reduced by the industrial truck according to the invention.
Since the pallet holders can be brought into and out of engagement with the pallet by means of a movement perpendicular to the direction of travel, i.e. the longitudinal direction of the industrial truck, the pallet holders can be implemented in the vertical direction of the industrial truck, without a constant back and forth movement of the truck. This contributes to significantly faster and easier handling of the pallets, i.e. it allows the formation of a pallet stack or pallet-by-pallet removal of an existing pallet stack in a relatively short period of time. Therefore the industrial truck according to the invention allows efficient handling, particularly of empty pallets.
As explained above, the time expenditure in connection with the activities involved in the handling of empty pallets can be significantly reduced by means of the industrial truck according to the invention. This in turn means a significant savings in personnel and personnel costs. Therefore a shipper of piece goods that has to handle a daily turnover of approximately 300 to 400 empty pallets and more can guarantee better working conditions.
Furthermore, since components of conventional industrial trucks can be used to a great extent, the production costs or acquisition costs for the industrial truck according to the invention are not higher than those for a conventional electric pole-arm forklift truck (xe2x80x9cantxe2x80x9d).
The industrial truck according to the invention can therefore be implemented as a stand-alone device or in the form of a special attachment for a wheel-supported stacker, counterweight stacker, or reach mast truck.
Although the industrial truck according to the invention is specifically designed for handling empty pallets of a certain format, particularly so-called euro-pallets, it can fundamentally also be used for transporting any desired kind of pallet, a load packed on a pallet, or a stack of pallets.
Further developments and embodiments according to the invention are the object of the dependent claims.
In order to be able to pick up and lift an empty pallet that is lying on the floor, the load arms have to be adjustable, depending on the format of the pallet to bepicked up, both with regard to a certain distance from the floor and with regard to a certain distance from one another. In order not to limit the use of the industrial truck according to the invention to a certain pallet format, it is therefore advantageous if the load arms that hold the pallet holders are adjustable horizontally and vertically.
Irregardless, the load arms can be provided on a load carriage that can be moved vertically, as in the case of a counterweight stacker, a wheel-supported stacker, or a reach mast truck, which carriage can be moved up and down along a reach mast that is assigned to the load part or, as in the case of a forklift truck, an electric manual lift truck, or an electric pole-arm forklift truck, they can form wheel arms of the load part, which are supported on the floor by way of load rollers, where the load part can be raised, relative to the drive part, pneumatically, hydraulically, or mechanically. Furthermore, the load arms can be adjustable in the crosswise direction of the industrial truck. These measures make a significant contribution to great flexibility and therefore to a broad spectrum in the area of application of the industrial truck according to the invention.
In order to keep the risk of damage as low as possible when picking up the pallets, the pallet holders furthermore preferably have a rotation-mounted contact roller at their end facing the pallet, which contacts the pallet when the pallet holder is engaged with it. A relative movement between the pallet holders and the pallets therefore takes place by means of a roll-off movement of the pallet holder on the pallet. As a result, the friction forces that occur during a relative movement are significantly reduced, on the one hand; on the other hand, the likelihood of damage caused by a thrust impact is reduced, as compared with sharp fork prongs.
Such damage can be restricted even more if at least the outside circumference region of the contact roller is made of an elastic and therefore impact-absorbing material. Another advantage of this structure of the contact roller, particularly in the case of a heavy pallet stack that consists of a large number of pallets, is that the contact surface of the bottom-most pallet, which rests directly on the contact rollers, is increased relative to the pallet material, because of the resilience of the elastic material, which means that the contact roller presses into the pallet material to a lesser degree.
In order to allow problem-free handling of the pallets, even by a group of persons with less skill, it is furthermore advantageous if the industrial truck according to the invention has a feed device that makes it possible to guide and place an empty pallet that is lying on the floor, for example, between the two load arms with the pallet holders, while the industrial truck is in travel mode, by simply xe2x80x9crunning overxe2x80x9d the pallet to be picked up with the industrial truck, i.e. collecting it. In this regard, it is particularly advantageous if this feed device extends beyond the load part and the drive part of the industrial truck according to the invention, which means that collecting a pallet that is lying on the floor, for example, is not limited to forward travel of the industrial truck, but rather is also possible during reverse travel.
This feed device preferably comprises guide rails assigned to the load arms, which are aligned in the longitudinal direction of the industrial truck, where the distance between them, viewed in the direction of travel of the industrial truck, increases towards the front and rear of the industrial truck. With this feed device, pallets that are lying around on the floor can simply be xe2x80x9crun overxe2x80x9d, i.e. collected. The guide rails, in turn, can have a plurality of guide rollers arranged at a distance from one another in the direction of travel, i.e. the longitudinal direction of the industrial truck, which minimize the friction forces that occur between the guide rails of the feed device and the pallets when the pallets are run over and collected.
Another simplification in the collection of pallets results if the feed device has a locking device, preferably provided on the guide rails, which makes it possible to releasably lock the pallet to be picked up in place in a predetermined holding position between the two load arms. In this case, the industrial truck does not have to be stopped after it runs over a pallet, in order to pick it up, i.e. to take hold of it and lift it. Instead, the pallet to be picked up is pushed along in the travel direction of the industrial truck for a short distance, until it is removed from the floor, since it is held in place in a predetermined holding position between the load arms. By means of a corresponding adjustment of the speed of travel of the industrial truck, to a speed at which the pallet is picked up, i.e. taken hold of and lifted, by the two load arms, in this case the distance over which the pallet is pushed while it is lying on the floor can be minimized.
If, in addition to the locking device, a pick-up position sensor is also provided, which detects whether or not the pallet has taken the predetermined holding position, and indicates this by giving off a corresponding electrical signal, the operator of the industrial truck can effect pick-up of the pallet as a function of the electrical signal, by means of activating the load arms and/or the control device that is coupled with the holding position sensor. Of course, it is advantageous, in this regard, if the control device automatically activates the load arms and/or the pallet holders as a function of the electrical signal, since in this case the operator of the industrial truck only has to pay attention to running over the pallets to be collected with the shortest possible path. Pallet-by-pallet distribution of the pallets already stacked in a stack on the floor is also particularly simple when using the control device.
A preferred embodiment of the industrial truck according to the invention consists of the fact that the load arms each comprise a rotation-mounted roller, the axis of rotation of which is aligned in the longitudinal direction, i.e. are structured in roller form, where the pallet holders preferably extend tangentially over the outside circumference of the roller, in each instance. By means of a synchronous, opposite rotational movement of the two rollers in a direction of rotation that is determined, in each instance, the pallet holders can be brought into engagement with the pallet to be picked up, in such a way that the pallet which is being picked up is already lifted to a specific height simply by the further rotational movement of the rollers. A further rotational movement of the load arms would have the result that the pallet holder goes out of engagement with the lifted pallet, which would cause it to fall to the floor.
Once the pallet holders have been brought into engagement with the pallet, however, lifting the pallet could also be brought about by a vertical movement of the load arms, i.e. lifting of the pallet could be achieved by means of a rotational movement of the load arms in combination with a vertical movement. Of course, the rollers must be positioned in such a way, relative to the floor and the pallet to be picked up, i.e. they must be adjusted by means of a horizontal and vertical adjustment of the load arms and/or the pallet holders perpendicular to the direction of travel, i.e. the longitudinal direction, so that when a rotational movement of the rollers occurs, the pallet holders do not touch the floor, on the one hand, and they can be brought into and out of engagement with the pallet to be picked up, on the other hand. In this connection, the diameter of the circle described by the ends of the pallet holders, in each instance, during a rotational movement of the rollers, must also be coordinated with the pallet format in each instance.
With regard to the most efficient handling of empty pallets that is possible, particularly with regard to unstacking an existing pallet stack, it is advantageous if the rollers each have a plurality of pallet holders spaced uniformly apart in the circumference direction of the rollers. In this case, but of course only if the rollers and/or the pallet holders are appropriately coordinated with the distance from the floor and the pallet format of the pallets to be picked up, a pallet stack can be formed from any desired number of pallets, or an existing pallet stack can be unstacked, within a relatively short period of time, by means of a synchronous, opposite rotational movement of the rollers in the direction of rotation determined in each instance.
Forming a pallet stack by means of the industrial truck according to the invention can be implemented, for example, in that individual empty pallets that are lying around on the floor are xe2x80x9crun overxe2x80x9d by the industrial truck according to the invention, in at such a way that they are placed between the two load arms by the feed device described above. After the predetermined holding position between the two load arms of the industrial truck has been reached, in which the pallet that has been collected is held in place by the locking device, specifically even if travel continues, which position is detected by the holding position sensor, the rollers are activated, preferably automatically, to put them into a suitable rotational movement. In this connection, the pallet holders engage into the collected pallet and take the pallet with them, in an upward direction, during the course of the further rotational movement of the rollers. As soon as this pallet has reached a height that is sufficient to place another pallet under the pallet that has been lifted, the rotational movement of the roller is stopped. Immediately after this procedure, the next pallet can be run over and collected. Only after it has been detected, once again, that the collected pallet has been placed in the predetermined holding position between the two load arms, the load arms are put into a rotational movement in the opposite direction, causing the first pallet to be set down on the collected pallet underneath it. Unhindered movement of the rollers in the opposite direction of rotation is only possible, however, once the pallet holders have come out of engagement with the pallet in the higher position, viewed in the crosswise direction. For this purpose, the pallet holders must be able to perform a horizontal movement perpendicular to the longitudinal direction, by means of which they are moved away from the pallet. This can be achieved in that they are coupled with the roller, in each instance, in wing like manner, in such a way that they assume the aforementioned tangential position under the effect of a bias force, and can be pivoted into a circumference position, counter to the bias force, in which they are essentially aligned in the circumference direction of the roller. The horizontal movement of the pallet holders could also be achieved, in general, however, if the pallet holders are rigidly attached to the load arms and the load arms are adjusted horizontally, perpendicular to the longitudinal direction.
The wing-like coupling of the pallet holders with the load arms is also particularly advantageous for unstacking empty pallets that have already been formed into a stack. For unstacking, the industrial truck according to the invention first picks up a stack of empty pallets, in that it activates the rollers in such a way that the pallet holders are brought into engagement with the bottom-most pallet of the pallet stack, by means of a rotational movement of the rollers in a certain direction of rotation, in each instance, and the pallet stack is lifted. After transport of the pallet stack to a desired location, the rollers are activated in such a way that they perform a rotational movement in the opposite direction of rotation, causing the entire pallet stack to first be set down on the floor. The rotational movement of the rollers is then continued until the pallet holders or, in the case of several pallet holders distributed over the circumference of the rollers, the next pallet holders, engage with the pallet lying in the second row, viewed from the floor up. Since the pallet holders are coupled with the roller, as described above, they can pivot towards the roller and glide along the pallet stack under the pallet that is lying in the second row, if they hit against the pallet stack from the top, in each instance, during this continued rotational movement of the rollers. If the pallet holders are rigidly attached to the rollers, the load arms and/or the pallet holders must, of course, perform a horizontal movement perpendicular to the longitudinal direction. Now the rollers are activated again, in such a way that they perform a rotational movement in the first direction of rotation, in order to lift the pallet stack, starting from the second pallet, viewed from the floor up, thereby releasing the bottom-most pallet and making it possible to leave it behind.
Forming a pallet stack, or unstacking individual pallets from an existing pallet stack, could also be implemented in a different way, however. For example, the load arms could have a plurality of transport devices spaced apart in the longitudinal direction and aligned vertically, in each instance, with a transport means, such as a conveyor belt or a conveyor chain, on which the pallet holders are attached, in each instance. In this case, the transport means, in each instance, can be controlled to be synchronous in opposite directions. The pallet holders are aligned towards the pallet, preferably normally, on the transport means in each instance. Here again, it would be advantageous if the transport means each have a plurality of pallet holders, spaced uniformly apart in the direction of movement of the transport means, in each instance, and/or the pallet holders are coupled with the transport means, in each instance, in wing-like manner, as in the case of the roller, in such a manner that they assume the normal position under the effect of a bias force, and can be pivoted into a parallel position counter to the bias force, in which position they are essentially aligned parallel to the transport means.
The industrial truck according to the invention is particularly designed for handling empty pallets of a specific format, for example so-called euro-pallets. Therefore the industrial truck preferably has a holding device adapted to the format of the pallets, which is placed above the load arms and makes guided pick-up of empty pallets in the vertical direction of the industrial truck possible. On the one hand, this eliminates the risk of tipping of a pallet stack formed of several pallets. On the other hand, precise alignment of the pallets above one another is made possible.
In an advantageous further development, the holding device comprises a locking device, for example one or more spring-biased pivot hooks, which allow(s) releasable locking of the empty pallet(s) held in the guide basket at a certain height. This further development facilitates both the formation and the unstacking of a pallet stack, since it creates the possibility of holding the pallet stack in place, starting from any desired pallet, for example the second pallet from the bottom, by way of the locking device, while the bottom-most pallet can be set down on the floor, by means of the engagement of the pallet holders and appropriate control of the load arms. Subsequently, the pallet stack being held in place by the locking device can be taken over by the load arms again and the procedure described above can be initiated once again.